#Polyalphabetic cipher code

It appears to be a figure code as was becoming common at the time (see another article). Letters from Peter Morton, agent at Turin (Report p.vi), occasionally include words in cipher, of which a key is among the papers (Report p.12). Especially, the proper ordering in using the three tables is broken at least twice, as indicated with a check sign in the image to the right.) Lord Feilding's Correspondenceīasil Feilding ( Wikipedia) (styled Lord Feilding before succeeding his father as 2nd Earl of Denbigh) was King Charles I's ambassador to Venice, then Turin from 1634 to 1639 (Report p.vi, xi, xii).

(Several errors are found in the ciphertext. The ciphertext (as seen in an image at the county record office's website) is as follows (with nulls removed).Įt le paisant des gens sages, d'esprit, et de courage To add further security, the first and third words in every line are nulls (i.e., to be ignored). It can be seen that the same 'r' in the ciphertext may correspond to plaintext 's' or 'o' (or 'b' if the third table is used), which makes codebreaking difficult. The word 'soldat' becomes 'rrhiha' in the ciphertext. The first table was used again to encipher the fourth letter 'd' to 'i', and so on. To encipher 'soldat', the first letter 's', which is found to be paired with 'r' in the first table, is enciphered as 'r.' The next letter 'o' is sought in the second table and becomes 'r' the third letter 'l' becomes 'h' according to the third table.

The letter employs a polyalphabetic substitution cipher, which uses three substitution tables in turn.

Polyalphabetic cipher